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ZAlt?it
Patented Nov. 5, 1946
UNITED STATES PATENT‘ OFFICE
PREPARATION OF LACTATES.
John Leslie Jones, Toledo, Ohio, assignor ‘to
Libbey-Owens-Ford ‘Glass Company, Toledo,
Ohio, a corporation of Ohio
N0 Drawing. Application April 1, 1944
Serial No. 529,215
5 Claims. (01. 260-484)
1
2
ter 01" lactyl lactic acid' and the alkyl ester of di
lactyl lactic acid. Lactyl lactic acid is the prod
ing the. esters of lactic acid with allyl, crotyl,
uct of the esteri?cation of two, lactic acid mole
alpha-methyl allyl, methallyl, beta-chloro allyl,
cules, and dilactyl lactic acid‘ consists of a chain
beta-methyl crotyl, ethyl, propyl, isopropyl, pri
of three lactic acid residues formed bythe ester
mary butyl, secondary butyl and isobutyl alco
i?cation of three lactic acid molecules. It is be
hols.
lieved that the absence. of. unesteri?ed lactic acid
Because lactic acid is a hydroxy acid, mole
groups in‘ the residue prevents any esteri?cation
cules- of lactic acid may react with one another
reaction from taking place when the residuev is
to form esters and polyesters. Heretofore in the
preparation of a'simple ester of lactic acid, the 10 reacted: with alcohols in they presence of an alkoxe
ide. If any esteri?cation reaction tool; place,
reaction of molecules of the lactic acid with one
the
alkoxide would be destroyedv by the'Water
another has caused serious losses so that the yield
The invention relates to a method of prepar
of the simple ester has been relatively low.
The principal object oithe invention. is to pro
videa method of preparing simple esters of lac
tic acid in increased yields so as to render the
formed in 'such- an esteri?cation reaction._ 7
In the novel reaction that is, the subject of the
15 present invention, one of the’ reactants is the res-I
idue remaining'after the production'of a lactate
from alyl, crotyl, alpha-methyl allyl, methall-yl,
beta-chloro allyl, beta-methyl crotyl, ethyl, pro
Such esters are used as intermediates in the
pyLisopropyl, primary butyl, secondary butyl or
preparation of synethetic resins and other mate
rials. More speci?c objects and advantages are 20 isobutyl alcohol byesteri?cation with lactic acid.
production of such esters economically feasible.
The other: reactant. is one of said alcohols, which
apparent from the description which merely il
may not be the same alcohol used in the esteri?~
lustrates and discloses the invention and is not
cation» reaction by which the residue was formed.
intended to impose limitations upon’ the claims.
If it is desired to. react the residue with an alco
Heretofore a simple ester of lactic acid has
hol different from, the alcohol used in- the reac
been prepared by the conventional method of
tion by which the residue was formed, the alco
preparing esters, which consists in reacting the
hol reacted with the residue should have a boil
acid with the alcohol in the presence of an acid
ing point that is not substantially lower than the
catalyst while distilling off the water formed by
boiling point. of the alcohol used for the original
the reaction. Usually some of the alcohol dis
tills o? with the water, but a sufficient concen 30 esteriflcation reaction. If the» residue is reacted
‘with an alcohol having such a boiling point, a
tration of alcohol for the reaction may be main
substantial yield of the lactate of such alcohol
tained by adding some of the alcohol from time
may be recovered. By the use of an excess of an.
to time. After the evolution of water has ceased,
alcohol having a boiling point not substantially
unreacted alcohol may be distilled off and the
lower
than that of the alcohol used for the origi
ester that has been formed may also be obtained
nal esteri?cation reaction, the original alcohol
by distillation.
may be displaced from the residue by an ester in
At the end of such an esteri?cation reaction
there remains a considerable residue which can
not be further esteri?ed with the alcohol. Here~
terchangereaction and distilled off.
In the practice of the invention, it is prefera
tofore it has been considered necessary to dis 40 ble to use an. excess of the alcohol for reaction
with, the residue to produce a maximum yield of
card such residue, and the discarding of such
the. lactate of such alcohoh ‘ At they end of they
residue involves the loss of a considerable pro
reaction, the excess of the alcohol can be recov
ered by distillation before the ester is distilled
The present invention is based upon the dis
off.
45
covery that a substantial additional quantity of
Any alkoxide of a metal may be used as a
the ester can be recovered by reacting such resi
catalyst for the reaction. The common alkoxide
due with the alcohol in the presence of an alkox
forming metals are aluminum, alkali metals such
ide of a metal as a catalyst. An alkoxide can
as sodium and. potassium, and alkaline earth
exist only under anhydrous conditions, but the
residue left at the end of an ordinary esteri?ca 50 metals such as calcium and magnesium. These
metals are members of groups I, II and III of
tion reaction between lactic acid and an alco
the periodic system. The nature of the alkyl
hol is anhydrous because of the removal of water
radical of the alkoxide does not make any dif
during the reaction. It is believed that such a
ference, because the alkoxide of the alcohol to
residue is free from unesteri?ed lactic acid resi
dues, and comprises mainly lactide, the alkyl‘ cs 55 be reacted with the residue is always formed in
portion of the lactic acid employed.
3
2,410,740
the reaction solution. The proportions of dif
ferent alkoxides used may be varied widely. In
each case any appreciable catalytic proportion
may be used.
The reaction may be carried out at various
temperatures, but it is preferable to autoclave the
reactants to produce the maximum yield most
rapidly. If the alcohol used for the reaction is
different from the alcohol employed for the orig
inal esteri?cation reaction in which the residue
was formed, distillation to remove the alcohol
used for the original reaction, either at atmos
pheric pressure or under a vacuum, may be begun
as soon as the reactants arebrought together.‘
4
the metallic sodium or magnesium, an equal
weight of aluminum tri-(n-propoxide) may be
used. In place ‘of the allyl alcohol there may be
employed an equivalent amount of crotyl, alpha
methyl allyl, methallyl, beta-chloro allyl, beta
methyl crotyl, ethyl, propyl, isopropyl, primary
butyl, secondary butyl or isobutyl alcohol.
Various embodiments of the invention may
be devised to meet various requirements.
Having described my invention, I claim:
1. A method of preparing the esters of lactic
‘ acid with allyl, crotyl, alpha-methyl allyl, meth
_ allyl, beta-chloro allyl, beta-methyl crotyl, ethyl,
propyl, isopropyl, primary butyl, secondary butyl
If loss of the reactant alcohol takes place, some 15 and isobutyl alcohols that comprises reacting one
of the alcohol may be added from time to time
of said alcohols, in the presence of an alkoxide
to maintain an adequate concentration thereof
of a metal as a catalyst, with the anhydrous dis
Example
tillation residue remaining after the production
of a lactate from one of said alcohols by esteri?
A commercial aqueous solution of lactic acid
may be distilled at atmospheric pressure in a 20 cation with lactic acid.
2. A method of preparing the esters of lactic
substantially neutral condition to remove water
acid with allyl, crotyl, alpha-methyl allyl, meth
preparatory to esteri?cation of the lactic acid.
allyl, beta-chloro allyl, beta-methyl crotyl, ethyl,
Preferably the distillation of water is continued
propyl, isopropyl, primary butyl, secondary butyl
until the composition, calculated on the assump
tion that only simple lactic acid is present, con 25 and isobutyl alcohols that comprises reacting an
excess of one of said alcohols, in the absence of
sists of 100 per cent lactic acid. To this product
water and in the presence of an alkoxide of
is added from one and one-half to three equiva
a metal as a catalyst, with the anhydrous dis
lents of allyl alcohol, and an acid catalyst con
tillation residue remaining after the production
sisting preferably of a weight of a strong mineral
30
acid such as concentrated sulfuric or phosphoric
acid equal to 025-111 per cent of the weight of
lactic acid employed. From 100 to 200 cc. of a
of a lactate from one of said alcohols by esteri
?cation with lactic acid.
3. A method of preparing the esters of lactic
acid with allyl, crotyl, alpha-methyl allyl, meth
water-entraining liquid such as isobutyl ether,
n-butyl ether,'_benzene, toluene or a petroleum 35 allyl, beta-chloro allyl, beta-methyl crotyl, ethyl,
propy, isopropyl, primary butyl, secondary butyl
solvent may be added for each equivalent of
and isobutyl alcohols that comprises reacting one
lactic acid to assist» in the removal of water.
ofrsaid alcohols, in the presence of an alkoxide
Distillation is then carried out, preferably at
of a metal as a catalyst, with the anhydrous dis
atmospheric pressure, allyl alcohol and entrain
ing liquid being added from time to time to main 40 tillation residue remaining after the production
of a lactate by carrying to completion the esteri
tain an adequate concentration thereof. When
fication reaction of lactic acid with an excess of
evolution of water has ceased, the composition
preferably is neutralized by addition of a base
such as sodium acetate, calcium carbonate or
one of said alcohols.
‘
mm.'absolute pressure. The maximum yield of
allyl lactate that can be obtained by the fore
and isobutyl alcohols that comprises reacting an
> 4. A method of preparing the esters of lactic
sodium carbonate, and the excess of allyl alcohol 45 acid with allyl, crotyl, alpha-methyl allyl, meth
allyl, beta-chloro allyl, beta-methyl, crotyl, ethyl,
may: be distilled off at atmospheric pressure.
propyl, isopropyl, primary butyl, secondary butyl
The allyl lactate may then be distilled oil’ at 5-25
excess of one of said alcohols, in the absence
going, procedure is about 75 per cent. To the 50 of water and in the presence of an alkoxide of
a metal as a catalyst, with the anhydrous dis
residue remaining after the distillation of the
tillation residue remaining after the production
allyl lactate is added from one-half to ?ve times
of a lactate by carrying to completion the ester
its weight of dry allyl alcohol and from 0.1 to 2.0
i?cation reaction .of lactic acid with an excess of
per cent of its weight of metallic sodium or
magnesium. A maximum yield of allyl lactate 65 one of said alcohols;
5. A method of preparing allyl lactate that
may ‘then be produced by re?uxing for about 15
comprises reacting lactic acid with allyl alcohol
hours. The allyl lactate may then be recovered
in the presence of an acid catalyst and distilling
as in the preceding stage (after ‘neutralizing the
to produce an anhydrous residue free from un
composition, if desired) by‘distilling o? the excess
esteri?ed lactic acid residues, and reacting said
of allyl alcohol, and then distilling oil‘ the allyl
anhydrous residuewith allyl alcohol in the pres
lactate under vacuum. ‘By this second reaction
ence of an alkoxide of a metal as a catalyst.
the yield of allyl lactate may be increased to 90-95
percent. In the foregoing example, in place of
JOHN LESLIE Jonas.